that also has to do with at which point does the tester want to deem those differences negligible. if the movement of the paintballer is oversimplified, then you might overestimate the required bps; on the other hand if you account for the joints and movements of the paintballer then your test result would only apply to when the paintballer runs in that exact way and posture. practically i think the former is better.

Wait, I'm talking about the 'theoretical math'- Testing is done as punkworks did with whatever modifications to the test as one sees fit. For example, a larger sample size of runners of similar speed and build to account for different joint positions while crossing the lane. Or, the same individuals but running the same BPS lane from different starting distances (so that they're joints are more likely to be in a different position from attempt to attempt).